The present invention relates to a drive system for use in an information recording/reproducing apparatus.
Various disc drive apparatus have been devised hitherto with a view to reducing the demand (consumed electric power). A first known technique, as disclosed in the Japanese Utility Model Publication No. 3-25348, is that in a magnetic disc drive apparatus the servo signals and the data signals are alternately disposed so that in the non-selected state the reproduction circuit is operated only at the timing of the servo signal in movement of the head to a given track and the power supply to the reproduction circuit is stopped in the other data intervals. A second conventional technique involves drive-controlling a spindle motor for a magnetic disc by detecting the back electromotive voltage of the motor without using a position detecting element such as a Hall device, as disclosed in the Japanese Patent Provisional Publication No. 3-7809 (U.S. Pat. No. 5,036,264) where in start the winding is compulsorily energized with the open loop by means of an external oscillation start circuit. A third prior art technique involves the control of the motor due to the back electromotive voltage, i.e., the drive method of the brushless DC motor not having a position detector, as disclosed in the Japanese patent Provisional Publication No. 2-146590. In addition, a fourth prior art technique, i.e., the Japanese patent Provisional Publication No. 2-190973, discloses a technique for the demand reduction by two control modes to be taken at start and after the start and a fifth conventional technique, i.e., the Japanese Utility Model Provisional Publication No. 3-20094, discloses a spindle motor allowing a size-reduced and thickness-reduced hard disc drive (HDD) apparatus.
However, there are problems which arise with such conventional apparatus in that 1) the power supply voltage is required to be above 5 V whereby a small-sized battery or batteries become inapplicable to the drive of the apparatus; 2) the power consumed in a logic portion such as a logic IC is substantially a loss component such as Joule heat and the demand is great; and 3) the power supply voltage range for the operation is as narrow as 5 V.+-.5% (.+-.10% at the most). These problems substantially occur due to the ability of the battery. Generally, the discharge characteristic of the Ni-Cd battery which is widely used is that the voltage is lowered in accordance with the passage of time and a rapid discharge occurs from the vicinity of 1.2 V for only 2 or 3 hours as illustrated in FIG. 9A when continuously supplying a current of 400 mA. Further, the capacity of the battery decreases due to the self-discharge as illustrated in FIG. 9B. This is because the voltage varies in response to the variation of the load (current) and the internal heating amount becomes large in response to increase in the current.